Why does my knee hurt more when I go up the stairs instead of down them?

The pain in my knee is not only on the stairs its when I run and also sometimes even when I sit idle for long periods of time. The pain is just above my knee cap right at the top of the joint the pain radiates down through the center of my knee. Ive been an active duty Marine for the last 10 years with multiple combat tours carrying lots of heavy weapons and ammo long distances.

It sounds very much like what you are experiencing is runner's knee, known formally as patellofemoral pain syndrome. It is really classic of patellofemoral pain syndrome for their to be differential pain with certain activities, especially pain with sitting is quite classic.
Patellofemoral pain syndrome is essentially caused by improper gliding motion of the patella (knee cap) over the underlining leg bones (femur). This leads to pain and can cause some deterioration of the cartilage on the undersurface of the kneecap, worsening the pain.
There is no instant cure for patellofemoral pain syndrome, and surgical options while they do exist are usually not needed or helpful. The first step is to cut down on the high-impact exercise regimen that provokes the pain, as rest is essential to recuperation. Additionally, sometimes wearing a knee brace can help. In some people, over pronation at the foot is a factor which worsens or contributes to the pain, so wearing an orthotic shoe or a properly fitting athletic shoe can help. Finally, quadriceps strengthening exercises can be quite helpful, keeping in mind that all strengthening exercises should be performed with the leg straight (remember how it hurts when you have the knees bent while sitting or climbing stairs).
Talk to your primary care doctor if the pain persists.

This answer is for general informational purposes only and is not a substitute for professional medical advice.

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